Collagen degradation is involved in a variety of processes, including bone resorption and tumor metastasis. In vitro assays of the collagen-degrading activity of osteoclasts, for example, are invaluable to the discovery of drugs for the treatment of osteoporosis. “TRAP” (tartrate-resistant acid phosphatase) assays detect acid phosphatase produced by mature osteoclasts via either histochemical or immunohistochemical staining. Other existing assays use synthetic calcium phosphate-based matrices as a surrogate bone substrate to detect osteoclast activity, and culture dishes coated with calcium phosphate upon which osteoclasts can be cultured are commercially available.
Some assays use slices of either dentine or bovine cortical bone as a surrogate bone substrate. Stearns, Clin Exp Metastasis. 1998 May; 16(4):332-9, discloses an assay in which osteoblasts first are cultured with 3H-hydroxyproline. The osteoblasts produce 3H-collagen, which is deposited together with other matrix proteins on a culture plate surface. The osteoblasts are removed, and other cells can then be tested for the ability to degrade the deposited 3H-collagen.
Tumor cells secrete collagenases which degrade extracellular matrix components and aid metastasis. Garbisa et al., Cancer Lett. 9, 359-66, 1980; Liotta et al., Cancer Metastasis Reviews 1, 277-88, 1982. Cell-based assays for potential drugs that would block this process would be useful in identifying anti-metastatic agents.
There is a need in the art for sensitive and convenient cell-based assays of collagen degradation that can be used for rapid screening of potential therapeutic agents.